She says Mr. Yang was arrested on suspicion of illegally crossing borders and other criminal acts. She says his detention is not arbitrary, nor a violation of law, and says China is a country ruled by law.

International legal experts and officials of the U.N. Commission on Human Rights say Mr. Yang's detention violates both Chinese and international law. They say his family has received no notice of the charges against him, he has been held without formal charges longer than the law allows and he has not had access to a lawyer.

Mr. Yang fled China after the 1989 Tiananmen Square protests that shook China's government. He later became a resident of the United States. At the time of his detention, he was using a friend's passport, while he covertly researched labor unrest in China.

Human rights activists and Mr. Yang's wife recently brought his case to global media attention in Washington. Forty members of Congress support a bill calling on the Bush administration to pressure Beijing to release the economist.

On Thursday, China also tried to deflect growing criticism on another human rights issue, Nepal's recent deportation of 18 Tibetans to China.

The Tibetans illegally left China and entered Nepal on their way to join the Tibetan exile community in northern India.

Thousands of Tibetans have fled this way since a failed uprising against Chinese rule of the territory in 1959. Beijing has recently increased pressure on Nepal to stop the refugee flow.

The Chinese Foreign Ministry says China is doing nothing wrong, and is merely working with its neighbors to stop the flow of illegal immigrants. Ms. Zhang says critics are trying to "politicize" the issue, and are interfering in China's internal affairs.